Nitrogen based single and dual expander processes were analyzed for efficiency improvement considering compression energy minimization as objective. The significant parameters of nitrogen single and dual expander processes were investigated for their effect on the compression energy requirement. Thereafter optimization of single expander process was performed using process knowledge and for dual nitrogen expander process a customized algorithm inspired by the knowledge of design variables process is devised. The optimization results, in the specific energy requirement of 0.7449 kWh/kg LNG for single and 0.5007 kWh/kg LNG for dual nitrogen expander processes. The optimization results comparison with previous published studies show a significant energy savings. Furthermore, the proposed optimization methodology is flexible to be extended for any kind of single and dual expander process. (C) 2015 Elsevier B.V. All rights reserved.